Background:
Bis(indolyl) methanes (BIMs) have a wide spectrum of applications in biomedicine
and agriculture as well as are present in natural products. These bisheterocyclic compounds
possess vast pharmacological, including antifungal, antitubercular, anti-inflammatory, antibacterial,
anticancer, anticonvulsant, antibiotic, antiviral, antimalarial, analgesic, and antidiabetic properties.
BIMs scaffolds have also been employed as selective optical chemosensors for detection of some anions
and cations with the naked eye. Because of the importance of these bisheterocycles, various methods
have been reported for their synthesis through reaction of indole derivatives and aldehydes or ketones.
Therefore, the synthesis of BIMs through different methodologies has received widespread attention
in the field of organic synthesis and medicinal chemistry.
Objective:
In this study, the catalytic activity of phthalimide-N-sulfonic acid (PISA) as an efficient and
safe solid acidic organocatalyst toward the synthesis of BIMs derivatives in ethanol is described.
Methods:
Indole derivatives (2 mmol), aryl/heteroaryl aldehydes (1 mmol), and PISA (10 mol%) were
mixture in ethanol. The reaction mixture was stirred at room temperature for the appropriate times.
After workup and separation of catalyst, the corresponding heterocyclic products were obtained
through recrystallization from hot ethanol.
Results:
The BIMs derivatives were easily obtained via Bisindolization Reaction (BIR) of two indoles
(2-methylindole and indole) with a series of aryl and heteroaryl aldehydes. The BIR was efficiently
catalyzed at room temperature using PISA as an excellent organocatalyst under optimized reaction
conditions.
Conclusion:
The reactions were implemented in simple manner and were completed within acceptable
reaction times. The expected BIM products were obtained in satisfactory yields. The catalyst can be
recovered and reused several times in the template reaction. This approach provides the benefits of
convenience, simple operational procedure, no use of hazardous organic solvents, cheapness and ease
of preparation of catalyst.
Crystal structure and Hirshfeld surface analysis of poly[[bis[μ4-N,N′-(1,3,5-oxadiazinane-3,5-diyl)bis(carbamoylmethanoato)]nickel(II)tetrapotassium] 4.8-hydrate]
